1. Field of the Invention
The present invention generally relates to light-emitting device (LED) display panel, in particular, to a LED displaying circuit.
2. Description of Related Art
As usually known, the LED such as organic LED (OLED) or micro-LED can be fabricated to emit red light, green light, or blue light, which is one of the three primary color lights. One pixel usually comprises three sub-pixels tightly put together as one pixel. The three sub-pixels respectively display the red light, green light, and blue light according to the gray levels. The primary color lights as displayed are mixed to form a displayed color for one pixel. A large number of pixels, corresponding to the resolution, are displayed to form a colourful image.
The gray level to the LED is achieved by control the driving current flowing through the LED. The stronger the driving current, the brighter the LED. So, the gray level for each sub-pixel in digital image is converted into a corresponding driving current to drive the LED.
However, the relation between the luminance and the driving current of the LED is not ideally linear. Particularly, when the driving current is low, the performance of the LED is not stable, and would have a large deviation for each sub-pixel.
The deviation for the sub-pixels at low driving current would influence the displayed color. Because the sub-pixels has low luminous efficiency at low driving current.
Further, the driving circuit would occupy a relatively large area of the total available circuit area. When the image resolution greatly increase, such as 4K resolution level, the driving circuit for each sub-pixel in total would consume a large circuit area. It would cause an issue in design when the image resolution in display quality is expected be higher and higher.